The present invention relates, in general, to methods for fabricating monolithic three-dimensional structures on a substrate, and more particularly to methods for fabricating optical couplers for integrated laser and waveguide structures.
Advances in the technology available for processing and fabricating semiconductor devices have allowed structures of various shapes to be formed on the surface of a wafer, as by the use of a variety of photosensitive materials applied to the surface of the substrate and various photolithographic processes for defining structures to be fabricated. For example, conventional photoresist materials can be spun onto a substrate surface and then exposed to light in specified regions, as through the use of photolithographic masks, to create patterns on the substrate after the photoresist has been developed. Such techniques may be used, for example, to fabricate integrated lasers and waveguides, including ring lasers with a variety of cavity configurations such as those described in U.S. Pat. No. 5,132,983 and in copending U.S. patent application Ser. No. 09/918,544, filed Aug. 1, 2001, the disclosures of which are hereby incorporated herein by reference. The development of these technologies and the capability of producing a wide range of laser and waveguide structures expands the prospective applications for integrated optical devices, and adds the attractiveness of greater manufacturability and reduced cost.
Optical couplers are conventionally used to couple light to and from integrated optical laser and waveguide devices; however, easy and efficient techniques for coupling such devices with external components such as optical fibers are not available. Although optical couplers of various designs have been developed, there is great difficulty in aligning such couplers with integrated optical devices and with external optical components such as optical fibers, and the resulting low yield produces high costs for such devices. Accordingly, a monolithic optical coupler having an arbitrary three-dimensional pattern would be very desirable, for it would enable cost effective, high yield fabrication of integrated optical components and their couplers to enable coupling of the devices with external components such as optical fibers.